Expansion joint and method of installing it



May 29, 1934. Y Q P EDMONDS 1,960,374

EXPIANSION' JOINT AND METHOD oF INSTALLING 1T Filed Jan. 31, 1935 r/ /J///I rrr Ej? A Patented' May 29, 1934 EXPANSION JOINT AND METHODINSTALLING IT George P. Edmonds, Wilmington, Del., assignor to BondManufacturing Corporation, Wilmington, Del., a corporation of DelawareApplication January 31, 1933, Serial No. 654,524

7 Claims.

My invention relates to an improved method of constructingsectionalpaving and likestructures and has to do, more particularly,with the formation of a more satisfactory expansion joint 5 for suchstructures than has been capable of attainment by the methods and meansheretofore employed.

In the construction of concrete roads and like structures, it has beenthe practice to form the structure in spaced sections with a fillerstrip of a deposit of4 filler material in the intervening spaces, thefiller being capable of yielding under the compressional strain imposedthereon by the expansion of the sections due to increase in temperature.As a rule, such expansion joints have-been constructed of plastic,substantially non-compressible ller material, a portion of which, underthe strain of section expansion, is unavoidably extruded from thediminished space between the sections. For instance, in constructingconcrete roadways, the space between the adjacent sections isusuallylled with asphalt or a more or less plastic compositionconsisting of cellulosic material or other inert ller material and abinder of asphaltum. Such fillers are not materially compressible, butare plastic, with the result that, when Vexpansion forces the end wallscf the sections toward each other and the width of the gap -or spacetherebetween is lessened, a portion of the plastic filler is displacedand iiows out above the normal road surface, lcreating an objectionableraised zone or 4rib at the joint. Frequently, it has been foundnecessary to go overroads of this character and remove some of the.plastic filler which has been forced out at the joint. Subsequently,when contraction of the road sections occurs due tocolder Weather,thespaces between adjacent sections are-widened, the material in the spacesis insufficient to ll the enlarged gaps, and 40 the material previouslyextruded from the spaces during Warmer weather, even though allowedtoremain on the road surface, does not return to the spaces, with theresult that unll'edgaps are created between the sections. Thesev gapsnot l only render the road surfa'cerough, but particles ofincompressible material gain entry into the gaps in lieu of the originali'lllerand, thereby, practically eliminate the expansion joints.Furthermore, some commonly employed fillers, such 5o asasphalt-impregnated roofing paper and the like, while theoreticallycapable of being compressed, in practice, because of intermixture withdirt and like non-plastic and non-resilient material, do so only underextreme pressures, with the result that expansion of the sections isoften sections, and slip it in place.

accommodated by the heaving thereof from they road bed'and the formationof cracks therein.y

Theoretically, in order to provide a satisfactory cork compositionjoint, it should be necessary merely to make a cork strip having athickne equal to the maximum width of the space between From thestandpoint of actual practice, however, such a method is extremelydifficult if not impossible of execution. In the first place, concretepaving is usually laid in comparatively warm weather, and the sectionsthereof are not contracted. Moreover, such paving is subject -to linearvariation in accordance with its moisture content. xIt is selfapparentthen, that a cork strip, installed as the gap filling element, eventhough initially snugly fitted and cemented in place will, after theadvent of colder and drier weather, no longer snugly ll the gap. Ayconventional cork composition filler strip-will not ll an expansion gapwhich has widened since the time the strip was placed. As a result, sucha strip becomes loose in the widened-gap.

' It is, accordingly, ajprimary objectof my invention to provide amethod of constructing expansion joints employing a cork or corkcomposition ller strip, which joint will be fully com-` pensating-thatis, will permit lthe sections to freely and easily expand to their fullextent in accordance with rising temperature, yet which will itselfautomatically and adequately expand to completely ll the widening gapbetween sections when they/ are contracting in accordance with decliningtemperature.

It is an object of my invention to provide a simple, easy andinexpensive method of making permanentv cork-strip expansion joints insectional paving and like structures, which joints, once installed,require no caulking or further special attention.

It is an object of my invention to provide a cork expansion joint stripfor sectional paving and like structures, which strip is inherentlyselfanchoring.

between pavement sections and preclude the weathering action thereof,and possible formation of ice therein.

Further objects, and objects relating to details and economies ofconstruction and use, will deflnitely appear from the detaileddescription to 2 s follow. In one instance, I accomplish the objects ofmy invention by the devices and means set forth in the followingspecification. My invention is clearly defined and pointed out in theappended claims.

A structure constituting a preferred embodiment of my invention isillustrated in the accompanying drawing forming a part of thisspecication, in which:

Figure 1 is an end view of the highly resilient cork compositionllerstrip employed in carrying out of my method, said strip being shown inits normal, uncompressed state;

Fig. 2 is a diagrammatic view of the same filler strip disposed in thepress, prior ,to subjecting it to lateral compression;

Fig. 3 is a diagrammatic View ofthe same filler strip and press, saidstrip being subjected to a compression stress `effecting its reductionto 50% its original thickness;

Fig. 4 is an end view of the same strip immediately after its removalfrom the .press where it has been subjected to a constant 50% reductionin thickness for a period of approximately twelve hours;

Fig. 5 is a cros -sectional View of the strip shown in Fig. -5 a fewminutes after its removal from the press and disposed in the gap betweena pair of concrete sidewalk sections; and

Fig. 6 is a similar cross-sectional view of the same. sidewalk sectionsand illler strip a few hours later, showing the strip expanded intocomplete lling and self-anchoring relation with the sections.

The same reference numerals refer to the same parts throughout theseveral views.

In its broader aspect my invention relates to the formation oflexpansion joints in sectional4 vpaving and like construction, such asfloors, sidewalks, and highways, and consists first in spacedly layingsections of such size and form that, within the extremes of temperatureto which the structure will be subject, expansion and contraction maytake place without heaving or cracking of the sections, and second, inpreforming, of cork or equivalent highly resilient material, a fillerstrip for each expansion gap` between adjacent sections, which strip hasthe characteristic of being temporarily of less thickness than theinstant or normal gap between the adjacent sections and of expandingafter insertion in the gap, thereby automatically filling the gap, andanchoring itself therein.

More specically, and as applied to Asectional concrete pavingconstruction, my invention consists first in laying concrete sections10, 11 of the usual form and size, and spacing the sections from eachother so that gaps 12 are provided therebetween which will accommodatethermal expansion of the sections under the temperature changes to whichthe paving will be subject. I n casting the sections in situ upon thepavement bed 13, the usual care must be taken to prevent the formationof a web or bridge across the gap which wouldv interfere with freeexpansion of the sections. 'Ihe width ofthe gaps will depend, amongother factors, upon the character of the material oflwhich the sectionsare formed, th coefficient of linear expansion thereof, the expectedmaximum variation in temperature, and the spacing between the joints. I

have found that, for general purposes and general conditions, a llerstrip 14 of highlyyresilient cork composition having a thickness ofthreefourths of an inch is very satisfactory. Such a.

heaving thereof from the bed. In using a filler strip of suchcomposition and dimension, it is necessary merely to provide expansiongaps at such intervals and of such width that, under maximum sectioncontraction, each gap will be slightly less than three-fourths of aninch andl under maximum section expansion each gap will be not less thanone-fourth of an inch. General experience with the expected temperaturevariation and the material of which the sections are made will enablethe builder to allow for thermal contraction subsequent to construction.Thus, the proper thickness of the gap form to be used, when castingsectional concrete paving, may be readily computed for any giventhickness of filler strip.

Although theoretically the strip 14 may be formed of virgin cork, suchcork cannot `readily be obtained in the vdesired size and length, andfor reasons of economy and serviceability, I prefer to make the strip ofcork composition consisting of comminuted or granulated corkagglomerated with a thermo-setting binder and .formed by moulding in anextrusion machine. A suitable composition which I have foundsatisfactory for the manufacture of ller strips adapted for use inaccordance with my invention consists of 300 pounds of comminuted corkagglomerated with a thermo-setting binder consisting of a phenoliccondensation product formed by the reaction of phenol and formaldehyde.This binder sets when heat is applied, for instance, in the extrusionmachine, and the resulting composition is compressible but not plasticor displaceable under pressure. As an enduring plasticizing agent, Iuse, in this mixture, some 60 poundsof diethylene glycol, which alsoserves as a softening agent for the cork particles 'and renders themmore flexible, with the result that the composition is more easilycompressible than pure, untreated virgin cork. To this mixture there isadded any one of the numerous lubricants used in the cork compositionart. The procedure employed in the manufacture of the composition fromthe above ingredients is preferably as follows: The phenol, formaldehydeand diethylene glycol are mixed and heated in a copper-jacketed kettle.When rthe mixture has ,reached the required temperature, sodiumhydroxide is added as a catalyst. The temperature is maintained andheating continued until a sample of the liquid will set, in boilingwater, in ten minutes. The reaction is then interrupted, and theintermediate product, which is a heavy liquid, is immediately mixed withthe cold ground cork in the proportion ofv about 160 pounds of theliquid to 300 pounds of the cork. These proportions may be varied,however. The mixture thus provided is then taken to the extrusionmachine, .ffor instance, such as shown in United States Letters PatentNo. 1,453,617, issued May 1, 1923. In such a machine the mixture isconfined in a mold at a temperature of about 300 F., which completes thereaction and causes the comminuted cork to be agglomerated by thebinder, providing a cohesive mass of the shape desired. 1

Instead of the binder mentioned in the above formula, any one of anumber of other thermoerine and ethylene glycol.

setting binding agents may be used for agglomerating'the -brk'particles.As an enduring plasticizing and cork-softening agent. other materialsmay be employed, among which are glyc- As has been heretofore stated, asuitable strip thickness for general application is three-fourths of aninch. The strip should preferably be as -deep as the thickness of thepaving section and should extend the full length of the expansion gap,the upper surface of the strip being iiush with the adjacent sections,and providing therewith, a substantially uninterrupted paving surface.It is obvious, of course, that the gap might, if desired, be filled withtwo or more strips, superposed, end on end, or side by side, one or allof which may be precompressed. While the strip may have any desiredcross-sectional form, for ease of application as well as simplicity ofmanufacture, I .have found the disclosed rectangular form to be entirelysatisfactory.

In accordance with my invention, the cork composition'strip 14 having anormal thickness of three-fourths of an inch is placed in a pressApressure of approximately 170 pounds per square inch. This pressure andreduction in thickness is maintained for a period ofl approximatelytwelve hours, whereupon the strip is removed. By means of the prolongedcompression of the strip to but its normal volume, upon release thestrip will not immediate-ly expand to Vits original normal thickness butwill, for some minutes thereafter, recover only some 45%of. its enforcedreduction in thickness, as shown in Fig. 4. Thus, the strip will have,for a short period after its removal fromthe press, a thickness of not.materially more than one-half of an inch, and if a gap of somethree-fifths of an inch has been provided between the sections, thefacile insertion of the strip in the gap, as. illustrated in Iig. 5, isassured. The partial paralysis of resiliency, or self-maintaineddeformation of the strip is, however, not permanent and usually in thecourse of less than one hour after its release from the press ,it Willhave eX- panded or recovered sufficient of its original nor- .malthickness to iill the gap and anchor itself itherein by frictionalcontact with the gap-delining end walls of the sections. `Such a strip,left to expand without restriction, will ultimately recover 95% or moreof its original thickness. It is important, therefore, only to becertain that the original thickness of the strip is vsome 5%.

greater than the maximum Width to which the gap between the sectionswill expand under lowest temperatures. 'ce

mal or original strip thickness. Generally speaking, the rate ofrecovery, both initial and ultimate is inversely proportional to thelength of time compression is maintained. A strip held under compressionfor two months initially recovered, upon release, but 58% its originalthickness. In less than one hour after release, it had recovered morethan 60% its original thickness. Some fifteen hours elapsed before ithad recovered of its original thickness. In four days it had recoveredsome, of its original thickness, and after one month it had expanded toapproximately its original thickness. The period of compression to 50%original'thickness, is therefore, not critical and may be varied inaccordance with requirements. strip of the specified composition maybesubjected to pressures either less or more than 170 pounds per squareinch, though not over a broad range comparable, to that relating to thetime factor. Cork strips of the composition specified have beensubjected to pressures amounting to thousands of pounds per square inch.There are limits, however, beyond which serious and more or lesspermanent impairment of resiliency results. ,Suiiice it to state thatpressures of from l to 150 pounds per square inch effect a substantiallyuniform progressive reduction in strip thickness; 150 pounds pressureper square inch effecting a reduction in strip thickness toapproximately 52% of normal. From 150 to 600 Likewise, a cork l poundspressure there is eiected a material though increasingly less markedreduction from 50% to 33% The pressure required. to effect greaterreduction in `thickness than 50%, as well as the permanent impairment ofresiliency resulting from greater compression, render more or lessundesirable the practice of my method loylythickness reductionsmaterially greater than 0 o. i v

I am aware that my method may be varied considerably without departingfromthe scope of my. invention. It may be employed in replacing orrenewing expansion joints in old structures as well as in theconstruction of new structures. Other materials such as virginl cork maybe used in the fabrication of the filler strip. Moreover, because ofirregularity of expansion gap width or unusual seasonalV variations intemperature, a strip of greater thickness than threefourths of an inchmay be desirable or necessary. I, therefore, claim my invention broadlyas indicated by the appended claims.

What I claim is: l

1. The method of, constructing sectional paving and like structurescomprising: laying sections of such size and form as can, within theextremes of temperature to which Fthe structure will -be subject, freelyexpand and contract without the development of destructive internalstresses, spacing said sections so that a substantial gap is definedtherebetween even when the sections are under maximum expansion,forming, of cork orequivalenthighly resilient material, a filler striphaving a normal thickness greater than thewidth of the gap defined bythe sections under maximum contraction, compressing said strip to suchan extent and maintaining said compression for such a period asto'effeet temporary, self-maintained deformation therein characterizedbya reduction in the thickness thereof to less than the normal width ofthe gap defined by said sections, placing said stripin said gap Whilestill in its temporary,

Y s id strip to expand and fill said gap.

2. The method of constructing sectional paving and like structurescomprising: laying sections of such size and form as can, within theextremes of temperature to which the structure will be subject, freelyexpand and contract without the development. of destructive internalstresses, spacing said sections so that the width of the gap between thesections under maximum expansion will not be materially less thanonethird the width of the gap defined by the sections under maximumcontraction, forming, of cork or equivalent highly resilient material, afiller strip having a normal thickness greater than the width of the gapdefined by the sections under maximum contraction, compressing saidstrip to such an extent and maintaining said compression for such aperiod as to effect temporary, self-maintained deformation thereincharacterized by a reduction in the thickness thereof to` less than thenormal width of the gap defined by said sections, placing said strip insaid gap while still in its temporary, self-maintained, deformed state,and allowing said strip to expand and fill said gap.

3. The method of constructing sectional paving and like structurescomprising: laying sections of such size and form as can, within theextremes of temperature to Jwhich the structure will be subject, freelyexpandfand contract without the development of destructive internalstresses, spacing said sections so that the width of the gapbetween thesections under maximum expansion will not be materially less thanonethird the width of the gap defined by the sections under maximumcontraction, forming, of highly resilient cork composition, a fillerstrip having `a normal thickness greater than the width of the gapdefined by the sections undermaximum contraction, compressing saidcorkstrip to such an extent and maintaining said compression for such aperiod as to temporarily paralyze its power of rapid recovery and effecta material though temporary self-maintained reduction in thickness toless than the normal width of the gap defined by the sections, placingsaid cork strip in said gap whilel still in its reduced state, andallowing said strip to expand and fill said gap.

4. The method of constructing sectional paving and like structurescomprising: layng sections of such size and form as can, within theextremes of temperature to which vthe structure will be subject, freelyexpand and contract without the development of destructive internalstresse spacing said sections so that the width ofthe gap between thesections under maximum expansion will not be materially less thanonethird the-width of the gap defined by the sections under maximumcontraction, forming, of highly resilient cork composition, a fillerstrip A having a normal thickness greater than the gap isgreater inwidth than the reduced thickness of said strip, and allowing said stripto. expand, ll said gap, and anchor itself in placel therein.

5. The method of constructing concrete high- Ways comprising: layingmonolithic slab sections having a length such that, within the extremesof temperature to which the highway will besubject, the maximum seasonalvariation in length due to thermal expansion and contraction will be notmaterially greater than one-half of an inch for each section, spacingsaid sections so' that a gap of at least one-fourth of an inch will bedefined between adjacent sections when under maximum expansion, forming,of cork composition compressible to substantially one-third its normal volume without permanent destruction of its resiliency, a filler striphaving a normal width of approximately three-quarters of an inch,compressing said strip to a width of approximately three-eighths of aninch, maintaining said com- .pression for such a period that theresiliency of said strip is temporarily paralyzed and when released andfor a short period thereafter, said strip will expand to approximatelybut threefourths its original normal thickness, releasing said stripfrom compression at a time when its thickness upon release would be lessthan the nstant width of said gap, and immediately placing said strip insaid gap and allowing'it to expand and anchor itself therein.

6. The method of forming resilient expansion joints in sectional pavingand like structures comprising: preforming, of `highly resilient corkcomposition, a filler strip having a thickness approximately five percent greater than'the width of the gap defined by the paving sectionsunder maximum contraction, compressing said strip so as to reduce itsthickness to substantially fifty per cent its original thickness,maintaining said compression for a sufficient period of time totemporarily paralyze the resiliency of the strip and cause it toinitially recover, when released, approximately but fifty per cent ofits reduction in thickness, placing said strip in the gap between saidsections shortly after it has been released and while its thickness isless than the width of said gap, and allowing said strip to recover asmuch of its original thickness as is permitted by said sections, therebyfilling said gap and anchoring itself therein.

tion in the expansion gap between adjacent sections o f a sectionalpavement or similar structure to provide, with said sections, a smoothuninterrupted surface under all actual conditions of section expansionand contraction comprising: a strip of cork composition consisting ofhighly resilient comminuted cork particles agglomerated with a binder,the corkparticles of which have been highly compressed in one directionand thereby strained to such an extent as to have temporarily lost theircharacteristic property of rapid recovery to original size'whenreleased, said strip being of slightly less thickness than the width ofthe expansion gap for which it is adapted, and having thecharacteristic, if `lexternally unrestricted, of gradually expanding toa thickness of approximately per cent of its initial thickness'wherebywedging or anchorage between the callyv effected by simply laying thestrip therein before said expansion has taken place.

GEORGE P. EDMONDS.

paving sections defining the gap may be automati-

